This invention relates to musician's drums.
Typically, a modern day drum, comprises an open-ended cylindrical shell either of metal or, in the larger sizes, of wood and two vellum or plastics diaphragms stretched across each end of the shell.
Usually each diaphragm is furnished with a stiff enlarged rim permanently secured to the main sheet of the diaphragm. The inner diameter of the diaphragm rim is slightly larger than the outer diameter of the shell and each diaphragm is held in place on the shell by means of a clamping ring structure which rests upon the rim of the diaphragm and is loaded in the axial direction of the shell by means of a plurality of tensioning devices extending from the clamping ring structure to anchorages secured to the outside of the shell.
Typically, those anchorages comprise metal blocks bolted to the shell intermediate its ends. In relatively shallow drums, there may be one ring of anchorages at the mid-height centre of the shell with tensioning screws extending in both directions from each anchorage to each clamping ring structure. In deeper drums it is more usual for there to be two rows of anchorages, one row associated with one diaphragm and the other row associated with the other diaphragm.
It must be remembered that it is usual for the tension in one diaphragm to be different from that in the other. Therefore the tension in the tensioning screw for the respective diaphragms do not counter-balance each other and thus there is a need for rigid securement of the anchorages to the shell even in those instances in which a single row of anchorages is utilized.
The primary source of noise from a drum is of course the vibration of the diaphragms, one as a result of it being struck by the drumstick or the like and the other as a result of sympathetic induced vibration, but the present invention springs from the discovery that the shell in most cases is also capable of resonant vibration and can add materially to the tone and output of the drum if it is free to vibrate. In the typical prior art drum described above the vibration of the shell is minimized or damped by virtue of the heavy metal block anchorages secured to the shell and the fact that those anchorages are held quite firmly in place relative to the shell ends by the tensioning screws.